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Originally Posted by clownboy
Great article, thanks Francois. This part struck me as odd though. I mean, isn't the water flowing naturally through the tar sands already toxic? Aren't the tar sands areas already an uninhabitable moonscape? And don't tar sands give off CO2 naturally when heated by the sun?
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Tar sand is a mixture of clay and sand and very heavy oil. In order to get the oil out of the sand, the viscosity of the oil needs to be reduced, and this can only happen either at high temperature or by adding chemicals, or both. The tar sand is heated and/or mixed with suitable chemicals, and then water is flushed through it at high pressure to wash the oil out of the sand.
It takes lots of water to separate the oil from the sand, and that water is then contaminated, much more so than by flowing naturally (at atmospheric pressure, ambient temperature, and without added chemicals) through the sands. Actually, water has flown naturally through these sands for ages without being able to wash the heavy oil out of the sand.
The tar sands aren't necessarily just sands. They may also be below the surface. There may actually be top soil and vegetation covering these sands up naturally. Yet in order to produce the oil, large amounts of sands need to be processed. This leads to huge strip mines ... that indeed look like moonscapes.
The CO2 is a different matter altogether. Whenever you burn fossil fuels, you release CO2 as a by-product. You may be able to capture it again before it escapes into the atmosphere. There are several projects in the works for building coal firing power plants with carbon capture, although none of these projects has been able to come up with a solution yet that truly works.
There are several plants in various stages of completion that are able to get the CO2 separated out at acceptable cost (i.e., without reducing the EROEI too much), but the results are large quantities of CO2 (megatons of it) that noone knows what to do with. Some projects suggest to pump the CO2 deep into the ground, others suggest to use it to increase the pressure in ageing oil wells. Yet at the current time, it would be illegal in most countries to implement either of the two approaches. Hence carbon capture is still a bit of a pipe dream.
We may be able to survive global warming caused by conventional oil, because the oil will run out before global warming becomes too much of a problem. However, if we then switch over to burning all of the remaining coal as well, and then switch over to tar sands and oil shale, we may indeed release enough CO2 into the atmosphere to make our planet uninhabitable. An increase of the CO2 content of the air by 100% may raise the average temperature of the planet by 6 degrees centigrade -- this is more than the difference in average temperature between the ice ages and now (about 4 degrees centigrade). If we increase the CO2 content of the air by 300%, the atmosphere starts to become poisonous to humans.